#include <bits/stdc++.h>

using namespace std;

ifstream f ("lupu.in");
ofstream g ("lupu.out");

const int NMAX = 1e5;

//sar din l in el luand cea mai buna optiune mereu cu un pq;
priority_queue<int> pq;
pair<int, int> v[NMAX+1];

int main()
{
    int n, x, l;
    f >> n >> x >> l;
    
    for(int i=1; i<=n; i++)
        f >> v[i].first >> v[i].second;
        
    sort(v + 1, v + 1 + n);
    
    int dmin = -1;
    
    long long ans = 0;
    int cnt = 1;
    
    for(int i=0; i<=x/l; i++){
        
        int dmax = i * l;
        
        while(cnt <= n and v[cnt].first <= dmax)
            pq.push(v[cnt].second), cnt ++;
            
        
        if(!pq.empty()){
            
            ans += pq.top();
            pq.pop();
            
        }
            
        
    }
    
    g << ans;

    return 0;
}